Our Catchments

Most of our east Hampshire river catchments have their headwaters within the hills and chalk geology of the South Downs National Park. They all flow south across the coastal plain to join highly designated coastal waters (the Solent Maritime SAC, Solent & Southampton Water SPA, Solent & Dorset Coast SPA, Portsmouth Harbour SPA, Langstone & Chichester Harbours SPA). Our rivers are sandwiched between two highly protected areas and have influence on life within both. They are characterful and each have their own rich and vibrant history.

Our east Hampshire catchment is challenged by the volumes of abstraction we are asking from it and is classified as an area of serious water stress. Despite these limited resources, and alongside existing pressures from nutrient enrichment, habitat deterioration or loss and poor water quality, they are still increasingly threatened by considerable development pressure and urbanisation.

Here’s a glance at each river catchment in our patch, but watch out for deep dives in our news reel for special reports on each one…

River Hamble

Rising near Bishop’s Waltham from a plethora of chalk springs where the sand ‘boils’, the River Hamble runs for over 10km towards Southampton Water and the Solent. The tidal limit is at Botley, about half way along the river, making its estuary a prominent feature of the river and renowned for its maritime history.

Its rainfall catchment area covers around 74km2, which includes its two main tributaries, the Horton Heath Stream and the Moors Stream. Land use is mainly rural in its freshwater sections but with significant and increasing urban development pressure in the lower catchment areas.

River Meon

Rising in East Meon, the River Meon forms the shape of a shepherd’s crook as it heads west then south through the chalk hills of the south downs. It is the longest of the east Hampshire rivers and displays chalk river habitats and conditions through much of its length before entering the Solent.

The Meon Valley Partnership has been supporting monitoring and projects in the river catchment and has its own page for more information here.

River Alver

Rising from a series of springs and surface water between HMS Collingwood and Chark Common, the River Alver gathers across a flat coastal plain. It runs for about 6.3km forming a wide green corridor through an otherwise urban area, including through the Alver Valley Country Park and out to sea at Stokes Bay via a tidal sluice.

River Wallington

Rising to the north of Waterlooville the river first flows west and southwest through the Southwick Estate after which it merges with the Potwell tributary from the east. It then flows south through Fareham where it enters Portsmouth Harbour.

Its catchment is urbanised but includes important floodplains and green corridors with the lower river supporting the annual migration of sea trout, salmon and eel.

Hermitage Stream

Rising from north of the Queen’s Inclosure area of Waterlooville, once a part of the historic Forest of Bere, it collects two tributaries on its way to the coast; the Park Lane stream and the Riders Lane stream.

Great care and support from the Friends of the Hermitage Stream has helped maintain awareness and improvement on the river with support from Portsmouth Water in removing invasive non-native species. Havant Thicket Reservoir is being built within this catchment and is looking to make considerable habitat improvements within the concrete channel of the stream in the next few years.

Lavant Stream

Rising in the hills the villages of Chalton or Idsworth in the South Downs, it has a large rain catchment of 74km2. The Lavant Stream, as its ancient name suggests, is supplied by a series of springs (lavants) from the chalk layers of the Downs all along its length, even to the southern side of Havant town.

The local plethora of clean water, chalk springs and the river itself were key reasons why Havant became a vibrant and economically important settlement. But the stream has been canalised, culverted out of site and built over, moved and mismanaged over time, especially in its downstream urban extent through Havant.

Coast and Harbours

Stretching from the River Hamble to Langstone Harbour, the eastern Solent is a rich and varied coastal landscape. This area includes saltmarshes, mudflats, shingle beaches, and sheltered estuaries—perfect homes for birds, fish, and marine life.

The mudflats and saltmarshes attract thousands of wading birds like curlews, oystercatchers, and redshanks. Seagrass beds and tidal creeks support fish nurseries, crabs, and even visiting seals. Langstone and Chichester Harbours are internationally important for overwintering birds.